The present invention relates to a semiconductor integrated circuit device and to a method of manufacture thereof; and, more particularly, the invention relates to a technique that is effective when applied to a semiconductor integrated circuit device using a so-called strained substrate, which is a substrate to which a stress has been applied at a surface portion thereof, and to a method of manufacture of the device.
Characteristics of a semiconductor element, such as a MISFET (Metal Insulator Semiconductor Field Effect Transistor), that is formed over the main surface of a semiconductor substrate are determined by various factors. When a tensile stress is applied to the surface layer of the substrate, the mobility of electrons in a channel region increases, which improves the current driving capacity of the MISFET.
Such a substrate is called a “strained substrate”. A description of a MOSFET using such a substrate can be found, for example, in Strained Si MOSFETs for High Performance CMOS Technology (2001 Symposium on VLSI Technology Digest, pp 59 to 60).